Droughts in semi-arid cereal regions of Algeria

The droughts in the semi-arid Algeria’s cereal regions are evaluated by studying the average monthly rainfall, from September to June, over the period (1941-2011), based on the firstorder Markov chain. This method traces rainy and dry days, cumulative rainfall and the probability of receiving rainfall above the thresholds of 0,1, 5, 10, 20 and 30 mm, in conjunction with the cereal development cycle. The rains analysed showed that the distribution of rainy days at the chosen thresholds did not exceed the variable averages of 6 to 9 days per month. These days are characterized by random cumulative rainfall, with probabilities fluctuating between + 40% and + 80%. Hard droughts affect seeding dates and yield factors for rainfed cereals.Keywords: Algeria, rainfall, Sowing, Markov Chai

Influence of nitrogen fertilization on lettuce yields (Lactuca sativa L.) using the15N isotope label

ArticleNitrogen fertilization plays an important role in the growth of market gardening and the improvement of yields. Its efficiency of use is imperative for the preservation of the agricultural environment. An experiment is carried out over three consecutive years (2014/2015), (2015/2016) and (2016/2017), in a sub humid climate. The methodology adopted focuses on the variation of optimal nitrogen doses and their effects on the evolution of lettuce cultivation (Lactuca sativa L.), which has a socio-economic impact. The approach takes into account the isotopic marking technique, 15N. The experimental device adopted is of the complete random block type, with four (04) levels: 0 (control), 60, 120 and 180 kg N ha-1 with four (04) repetitions. These levels are used to diagnose the effect of different doses on biomass (dry matter) and yield. It has been shown those doses between 0 and 120 kg N ha-1 increase significantly (p < 0.05), yields and dry matter with values of 18.32, 45.49 to 57.93 t ha-1 and 4.32, 5.52 to 9.77 t ha-1 , respectively. The rate of 120 kg N ha-1 , is shown statistically, as the efficient rate to cover the nitrogen needs of lettuce. This efficiency reaches 74.48%. Beyond that, nitrogen is not valorized by the crop. These results contribute to the realization of a technical reference system for lettuce cultivation, for an efficient use of nitrogen